scleroprotein


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scleroprotein,

large class of proteinprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
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 molecules that are ordinarily insoluble in water. The scleroproteins are employed principally for architectural purposes in the living cell and are localized in the structural tissues of bone, hair, skin, wool, silk, nails, hooves, and feathers. The major subclasses of scleroproteins include the collagenscollagen
, any of a group of proteins found in skin, ligaments, tendons, bone and cartilage, and other connective tissue. Cells called fibroblasts form the various fibers in connective tissue in the body.
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, elastins, and keratinskeratin
, any one of a class of fibrous protein molecules that serve as structural units for various living tissues. The keratins are the major protein components of hair, wool, nails, horn, hoofs, and the quills of feathers.
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Scleroprotein

 

(also albuminoid), a simple protein of animal origin that is insoluble in water and in dilute solutions of salts, acids, and bases. The most important scleroproteins are collagen, keratin, and fibroin. All scleroproteins have a fibrillar structure. When present in organisms in solid or plastic state, scleroproteins ensure the mechanical firmness of organs, protect the organs from effects of the environment, and form supportive reticulate structures within cells and membranes, influencing the permeability of the latter. In the natural state, scleroproteins (except elastin) are not hydrolyzed by proteolytic enzymes and therefore have no nutritive value.

Other examples of scleroproteins are reticulin, which is found in the skin of mammals, the proteins of byssus and gossamer, flagellin (in the flagella of thermophile bacteria), conchiolin (in the shells of bivalve mollusks), iodine-containing spongin (in marine sponges), and gorgonin and antipathin (in corals).

REFERENCES

Gaurowitz, F. Khimiia i funktsii belkov. [2nd ed.] Moscow, 1965. (Translated from English.)
Khimiia biologicheski aktivnykh prirodnykh soedinenii. [vol. 1.] Moscow, 1970.

E. N. SAFONOVA

scleroprotein

[¦skler·ō′prō‚tēn]
(biochemistry)
Any one of a class of proteins, such as keratin, fibroin, and the collagens, which occur in hard parts of the animal body and serve to support or protect. Also known as albuminoid.